1. Field of the Invention
The present invention relates to selective chemical milling of etchable metal-containing material supported on a web of non-metallic material, and more particularly to webs having functional and non-functional etch-resistant patterns or etched features and processes using or making same.
2. Description of Related Art
Functional patterns formed into aluminum foil are used in a variety of products, including microwave plates, trays and bowls, planar speakers, electronic circuitry surveillance products used for shoplifting prevention in retail environments, and flexible heaters, just to name a few. Common processes to form these products includes chemical milling or chemical etching. This chemical process can be described as follow. A metallic foil of desired thickness is laminated to a suitable substrate and patterns of desired design are printed onto the foil surface with an etchant resistant protective coating. These functional patterns typically are placed as closely together as possible, subject to the shape of the functional patterns and the spacing requirements imposed by such operations as cutting the rolled up web into segments for subsequent handling and processing, which occur after the chemical etching process. The printed metallic foil is then introduced to the etching solution, where upon the uncoated area will be etched away, leaving the desired protected features behind. The etching solution can be acidic or alkaline in nature, depending on the type of metal being etched. The metal foil can be of different thickness, depending on the intended function of the desired product. Typical foil thicknesses are from about 1 micron to about 15 microns and greater for microwave applications, from about 5 microns to about 50 microns and greater for planar speakers and flexible heaters, and from about 5 microns to about 70 microns and greater for electronic article surveillance products. The web may then be wound up into a roll, which may be cut up into segments for subsequent handling and processing.
An example of a web used for making security tags is disclosed in U.S. Pat. No. 5,754,110, issued May 19, 1998 to Appalucci et al. The security tag has a resonant circuit on one surface of a substrate, and a guard member that surrounds but is electrically isolated from the resonant circuit. In one embodiment the guard member is a discontinuous conductive member. In another embodiment it is a non-conductive member comprising the same material as the substrate. The guard member functions to electrically isolate the resonant circuit to facilitate testing of the resonant circuit during the manufacturing process when the resonant circuit is in web form. The web is processed to form the resonant circuits and the guard members for each of the tags on it by the continuous spray etching apparatus disclosed in U.S. Pat. No. 3,913,219, issued Oct. 21, 1975 to Lichtblau.
A particularly useful continuous demetallizing process and apparatus are described in U.S. Pat. No. 5,340,436, which issued Aug. 23, 1994 to D. Gregory Beckett. The apparatus has, generally speaking, an elongate tank that holds a bath of aqueous etchant material. The web containing the metal layer to be etched initially is arranged in a roll. The web is taken off of the roll and printed with a pattern of etch-resistant coating designs defining areas not to be etched. The web is then guided into the bath at one end, guided either horizontally or sinusoidally through the bath, and removed from the bath and taken up on another roll at the opposing end of the bath. The web is driven along its path by any suitable drive mechanism. An example of a drive mechanism is a combination of driven belts and roller elements. The web passes between these elements, which engage the web and drive it.
Although the Beckett demetallizing process is effective and economical, it is desired to make this demetallizing process and others even more effective and economical, especially when such a process is used to etch a web that contains a thick metal layer or that becomes flimsy and difficult to handle while passing through the etchant bath.
The present invention in one embodiment is a method of effecting selective demetallization of a web in an etchant bath to form a plurality of product units for products, the web having a layer of metal-containing material supported on flexible substrate layer. The method comprises establishing a pattern having a first part to define product units on the web, and a second part to define protected areas on the web outside of the product units for maintaining the etchant bath in a vital state over a long lifetime; placing etchant-resistant material on a first side of the web over the metal-containing layer in accordance with the pattern; passing the web in an immersed condition through the etchant bath to remove the metal-containing material from areas of the web not protected by the pattern; and removing the web from the etchant bath.
Another embodiment of the present invention is a method of effecting selective demetallization of a web in an etchant bath to form a plurality of product units for products, the web having a thick layer of metal-containing material supported on flexible substrate layer. The method comprises establishing a pattern having a first part to define product units on the web, and a second part to define protected areas on the web outside of the product units for preventing excessive heat generation in the etchant bath and maintaining the etchant bath stable and controllable; placing etchant-resistant material on a first side of the web over the metal-containing layer in accordance with the pattern; passing the web in an immersed condition through the etchant bath to remove the metal-containing material from areas of the web not protected by the pattern, whereupon the etchant bath is not overheated and remains stable and controllable; and removing the web from the etchant bath.
A further embodiment of the present invention is a method of effecting selective demetallization of a web in an etchant bath to form a plurality of product units for products, the web having a thick layer of metal-containing material supported on flexible substrate layer. The method comprises establishing a pattern having a first part to define product units on the web, and a second pan to define protected areas on the web outside of the product units for imparting predetermined flex characteristics to the web; placing etchant-resistant material on a first side of the metal-containing layer in accordance with the pattern; passing the web in an immersed condition through the etehant bath to remove the metal-containing material from areas of the web not protected by the pattern, whereupon the web acquires the predetermined flex characteristics; and removing the web from the etchant bath.
Placing etchant-resistant material on a first side of the metal-containing layer in accordance with the pattern; passing the web in an immersed condition through the etchant bath to remove the metal-containing material from areas of the web not protected by the pattern, whereupon the web acquires the predetermined flex characteristics; and removing the web from the etchant bath.
Yet another embodiment of the present invention is a method of effecting selective demetallization of a web in an etchant bath to form a plurality of product units for products, the web having a thick layer of metal-containing material supported on flexible substrate layer. The method comprises establishing a pattern having a first part to define product units on the web, and a second part to define protected areas on the web outside of the product units for preventing excessive heat generation in the etchant bath, maintaining the etchant bath stable, and controllable imparting predetermined flex characteristics to the web; placing etchant-resistant material on a first side of the metal-containing layer in accordance with the pattern; passing the web in an immersed condition through the etchant bath to remove the metal-containing material from areas of the web not protected by the pattern, whereupon the etchant bath is not overheated and remains stable and controllable, and the web acquires the predetermined flex characteristics; and removing the web from the etchant bath.
Another embodiment of the present invention is a metal-containing web comprising a substrate; a plurality of etched metal-containing first product units disposed on a first side of the substrate, adjacent ones of the first product units being contiguous over peripheral portions thereof and being separated over other peripheral portions thereof to gaps between the adjacent product units; and a plurality of first metal patches disposed on the first side of the substrate, at least one of the first metal patches being disposed in each of the gaps between the adjacent first product units to improve rigidity in the web.
Yet another embodiment of the present invention is a metal-containing web comprising a substrate; a plurality of etched metal-containing first features disposed on a first side of the substrate, each of the first features having a function in a product; and a metal-containing first field disposed on the first side of the substrate substantially throughout the web, at least a substantial portion of the first field having no function in a product and having discontinuities to establish predetermined flex characteristics in the web; wherein the first features are distributed through the first field.
A further embodiment of the present invention is a metal-containing web comprising a substrate; a plurality of etched metal-containing first features disposed on a first side of the substrate, each of the first features having a function in a product, and at least some of the first features being different than others of the first features; and a metal-containing first field disposed on the first side of the substrate substantially throughout the web, at least a substantial portion of the first field having no function in a product; wherein the first features are distributed through the first field.
Another embodiment of the present invention is a metal-containing web comprising a substrate; a plurality of etched metal-containing first features disposed on a first side of the substrate, each of the first features having a function in a product; and a metal-containing first field disposed on the first side of the substrate substantially throughout the web, at least a substantial portion of the first field having no function in a product; wherein the first features are distributed through the first field.